1. Technical Field
The present invention relates generally to communications systems, and in particular, to voice radio networks and associated devices. The present invention also relates to methods for routing voice calls over radio networks.
2. Related Art
Modern warfare, which typically involves the execution of tactics requiring pinpoint accuracy, relies heavily on sophisticated telecommunications systems to relay critical information between command and control centers, combat units, combat support units and combat service support units. The coordination of military action is often complicated because many such units may be dispersed over a wide geographic area, some of which may be of different types or specialties (e.g., infantry, armor, artillery, etc.), from different service branches, or even from different nations. Because of this diversity, the deployed telecommunications systems in any given combat zone may likewise be varied due to preference and/or suitability for the particular mission of the unit, staggered upgrade schedules, and so forth.
Combat-Net Radio (CNR) is a system widely used for remote communications to interconnect each of the aforementioned battlefield units. More specifically, CNR employs half-duplex communications typically implemented as a push-to-talk network. The CNR transceivers operate on a single radio frequency, or in the alternative, on multiple frequencies in a predefined sequence according to a frequency-hopping mode to prevent jamming attempts.
One specific implementation of CNR is the Single Channel Ground and Airborne Radio System (SINCGARS) currently utilized by United States and allied military forces. SINCGARS transceivers are capable of handling both voice and data communications, and are available in various form factors, including vehicle-mount, backpack, airborne, and handheld. Per its designation as CNR, SINCGARS is a half-duplex communication system that utilizes either a single frequency or multiple frequencies when operating in a frequency-hopping mode. Specifically, the VHF (Very High Frequency) FM (Frequency Modulation) band, designated as between 30 MHz to 87.975 MHz, is utilized by SINCGARS transceivers in incremental 25 kHz channels. Alternatively, the VHF AM (Amplitude Modulation) band, designated as between 108 Mhz and 151.975 MHz can also be utilized. In many implementations, the voice and data traffic between transceivers are encrypted for increased security.
Prior to the widespread deployment of SINGARS, a more basic VHF FM CNR system known as the AN/PRC (Army-Navy Portable Radio Communication) was utilized in the battlefield for tactical communications. The AN/PRC operated on frequencies between 30 MHz and 75.95 MHz with 50 kHz channels. Thus, although incompatible with the frequency-hopping mode of SINCGARS, an AN/PRC transceiver operating in the single frequency mode can communicate with SINCGARS transceivers. Accordingly, it continues to be utilized by military forces worldwide despite its legacy status.
In contrast to the SINCGARS and predecessor VHF FM radio systems described above, “net ready” telecommunications systems such as Link-16 and CDMA cellular phone networks utilize digital transmissions to carry a wide variety of data. Link-16, for example, is capable of transferring imagery data, text messages, and two channels of digital voice at different QoS (Quality of Service) levels. The underlying radio network is a Time Division Multiple Access (TDMA) scheme operating in the UHF (Ultra High Frequency) spectrum of 969 MHz to 1206 MHz. Because of its support for high speed, content-agnostic data transfers over a single communications channel, an increasing number of military platforms such as fighters, attack and EWACS aircraft, helicopters, ships, ground vehicles and the like have Link-16 capabilities. As utilizing a single network eliminates the need to carry and maintain separate equipment for each type of information exchanged, such systems are increasingly favored.
As can be appreciated from the foregoing, numerous standards and technologies for wireless communications are currently used in the battlefield amongst combat units. Such communications systems are often incompatible with one another, and there is accordingly a need in the art for linking all such systems such that any given transceiver can communicate with any other transceiver.